Is there any difference between "すみません"and "すいません"?

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there is no difference. It's just another way of saying the same thing... You could say that すいません is a "fast" way of speaking すみません

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There is no difference in meanings.

In a written language, it should always be written as "すみません" but the way it's pronounced is sometimes closer to "すいません".

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”すみません” is formal lines of "すまない."
”すいません” is slang word of "すみません."

In the most cases, people say "すみません" by ordinary.

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It's a little informal "すいません" than "すみません".